The following discussion of the background of the invention is merely provided to aid the reader in understanding the invention and is not admitted to describe or constitute prior art to the present invention.
Obstruction of the upper respiratory passages (referring to the nasopharynx, oropharynx, laryngopharynx, and larynx) can occur at any age. Those at risk for obstruction of some portion of the upper respiratory passages include persons with sleep apnea, those with airway tumors or foreign bodies such as aspirated food, and those with inflammatory or traumatic damage to the upper respiratory passages, which results in obstruction of the airway.
The medical sequalae of upper respiratory passage obstruction can be devastating: an inability to effectively ventilate the lungs rapidly produces hypoxemia, a generalized condition of lowered blood oxygen. If left uncorrected, hypoxemia leads to serious end organ injury such as stroke and myocardial infarction (heart attack), and may have a lethal outcome.
Snoring is a common chronic medical problem that is associated with episodic partial upper respiratory passage obstruction during sleep. Snoring afflicts millions of people worldwide. Snoring can lead to chronic fatigue that follows sleep deprivation and is considered by many to be a serious medical problem. The sound of snoring is produced by turbulent air-flow moving through an area of upper respiratory passages obstruction that produces resonant vibrations in the soft tissues, typically of the oropharynx.
A percentage of those who snore also suffer from sleep apnea, another frequent and serious medical condition associated with episodic upper respiratory passage obstruction. In the most common type of sleep apnea, obstructive sleep apnea (OSA), an afflicted individual sustains numerous episodes of apnea, or complete, and often prolonged cessation of breathing. Severe cases may have 100 or more apnea events per hour of sleep. OSA results in nocturnal hypoxemia, and leads to cognitive impairment, daytime somnolence, hypertension, increased risk of stroke and myocardial infarction, and insulin resistant diabetes mellitus. Untreated, OSA may result in premature death.
OSA is caused by occlusion of a portion of the upper respiratory passages, usually at the level of the orphharynx, during sleep due to either alteration in the mechanical properties of the tissues in or near the upper respiratory passages, and/or to disturbances in neuromuscular control over airway caliber. The immediate factor leading to collapse in the upper airway is a negative pressure in the airway that exceeds the ability of muscles in the airway to maintain an open state. Alterations in the mechanical properties of the upper respiratory passages, which predispose to collapse of the upper respiratory passages during sleep, may be caused by anatomical conditions such as large tonsils, or may be idiopathic. A variety of medical interventions have been shown to improve the mechanical properties of the upper respiratory passages and reduce sleep related airway closure. These include remodeling surgeries, medical devices that re-position the mandible, and continuous positive airway pressure (CPAP).
Unfortunately, all current treatments produce results that are far from optimal. Surgery and re-positioning devices are effective in only a minority of OSA patients, and the responders cannot be identified with certainty prior to initiating treatment. As a result, many people are subjected to painful and expensive procedures without benefit. On the other hand, CPAP is effective in the majority of OSA patients; however, the treatment is uncomfortable and not well tolerated during long-term use. A substantial number of patients given CPAP discontinue therapy within the first year after initiation.
CPAP works by delivering air at pressures above ambient pressure to the upper respiratory passages during sleep. Application of positive pressure to the upper respiratory passages acts as a “stint” and can retard the tendency of the upper respiratory passages to collapse during certain stages of sleep in OSA patients. In order to deliver higher than ambient pressures to the upper respiratory passages, the patient must wear a tight fitting mask covering the mouth and/or nose. This mask is connected to an air supply tube, and a variable pressure air pump. An additional component can be added which humidifies the air, to avoid desiccation of the upper respiratory passages during treatment. There are multiple sources of patient dissatisfaction with CPAP including difficulty of exhaling against the delivered air pressure, an uncomfortable face mask which may provoke feelings of claustrophobia, the noise of the air pump and the moisture of the humidification system. Additionally, the effects of device noise, mask exhaust, and user discomfort can substantially disrupt sleep patterns of a user's spouse or companion. Also, some CPAP units are not easily portable and limit patients' ability to travel.
Therefore, there is a pressing medical need to develop a means of ameliorating obstruction of the upper respiratory passages, which is both highly effective and well tolerated during chronic use.